The object of this contract is to provide a statistical and data management facility which will serve the entire AIDS Clinical Trials Group system. This facility will produce efficient and timely protocol development; it will assure the quality of all collected data; it will provide disciplined and uniform study monitoring; and will be responsible for prompt and thorough interim and final statistical analyses of all ACTG studies. In addition, the SDAC will provide leadership in statistical science for the development of broad research strategies for HIV infection; it will participate in the setting of scientific and administrative policy for the ACTG; it will develop novel methods of designing and analyzing AIDS clinical trials responsive to the particular needs of the ACTG; and will conduct cross-study analyses of the ACTG database, such as studies of the natural history of HIV or of prognostic factors for disease progression (such as CD4 levels or viral markers).